Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• equatorial position, placing the electronegative carbamate substituent and the C–O bond in the tetrahydropyran ring into a gauche orientation (Figure 1). We propose a chelated transition state for the formation of 19, 21, and 23 (Scheme 3). After the initial hydrozirconation and transmetallation with

Continuous flow enantioselective arylation of aldehydes with ArZnEt using triarylboroxins as the ultimate source of aryl groups

• Julien Rolland,
• Xacobe C. Cambeiro,
• Carles Rodríguez-Escrich and
• Miquel A. Pericàs

Beilstein J. Org. Chem. 2009, 5, No. 56, doi:10.3762/bjoc.5.56

• flow system for the synthesis of enantioenriched diarylmethanols from aldehydes is described. The system uses an amino alcohol-functionalized polystyrene resin as the catalyst, and the arylating agent is conveniently prepared by transmetallation of triarylboroxins with diethylzinc. Keywords

• have been explored as the ultimate source of aryl groups [24][25][26][27][28][29]. In these approaches generally good results have been obtained, but at the expense of using a large excess of diethylzinc for the transmetallation step, since two non-productive equivalents of the reagent are consumed in

• to be used in the reaction [30][31][32] (Scheme 2). This represents a highly atom-economical approach since, in principle, no sacrificial excess of diethylzinc is needed for the transmetallation process and up to a 74% of the molecular mass of triphenylboroxin (the less favourable example) can be

Preparation and Diels–Alder/cross coupling reactions of a 2-diethanolaminoboron- substituted 1,3-diene

• Liqiong Wang,
• Cynthia S. Day,
• Marcus W. Wright and
• Mark E. Welker

Beilstein J. Org. Chem. 2009, 5, No. 45, doi:10.3762/bjoc.5.45

• substituted dienes are stable but their organic solvent solubility is not ideal. Preparation of more highly substituted BF3 dienes also requires a transmetallation protocol which yields a Grignard-BF3 by-product which has to be separated from the desired diene [9]. To overcome these methodology challenges we

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• case to produce biphenyl. The yield of 4-methoxybiphenyl was increased by over 20% as seen in Table 1. However, while the yield of 4,4′-dimethoxybiphenyl almost doubled, the yield of biphenyl increased three-fold. If there was simple transmetallation occurring then there should be equity in the yields

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• from the stem bark of Asimina triloba as an inseparable mixture of 30S and 30R diastereomers [83]. In 1998, Marshall’s group reported the total synthesis of (+)-(30S)-bullanin (217) through SE2′ additions of oxygenated non-racemic allyl stannane (Scheme 29) [84]. Transmetallation of stannane 219 with

Mechanistic aspects of the isomerization of Z-vinylic tellurides double bonds in the synthesis of potassium Z-vinyltrifluoroborate salts

• Hélio A. Stefani,
• Rafael C. Guadagnin,
• Artur F. Keppler,
• Giancarlo V. Botteselle,
• João V. Comasseto and
• Carlos A. Suganuma

Beilstein J. Org. Chem. 2008, 4, No. 9, doi:10.1186/1860-5397-4-9

• features of the transmetallation with complete retention of the original double bond geometry, we report herein the synthesis of potassium vinyltrifluoroborate salts by means of the Te-Li exchange reaction. To the best of our knowledge, this is the first reported preparation of potassium E